Nov. 20, 1917 
Hydrocyanic-Acid Gas as a Soil Fumigant 
43i 
A series of experiments was therefore begun to determine the effect 
of water and of different soils on hydrocyanic-acid gas. Air from a 
jar containing 1.0 gm. of sodium cyanid and 15 c. c. of 10 per cent sul¬ 
phuric acid in 1 liter of water was aspirated through 5 c. c. of N/ioo 
iodin until the latter was decolorized, this requiring 468 c. c. of air. 
To determine the amount of gas absorbed by water, air from the same 
solution of hydrocyanic-acid gas as above was aspirated through 50 c. c. 
of water and then into iodin until the latter was decolorized, the result 
being that 3,456 c. c. of air decolorized 5 c. c. of N/ioo iodin. 
AIR ASPIRATRD DIRECTLY INTO IODIN 
It was found that 468 c. c. of air from the above solution decolorized 
5 c. c. of N/ioo iodin when introduced directly, while it was necessary 
to use 3,456 c. c. of air from the same solution to decolorize an equal 
amount of iodin when aspirated first through 50 c. c. of water, showing 
that the latter absorbed the gas from 2,988 c. c. of air, equivalent, ac¬ 
cording to the above data, to 31 c. c. of N/ioo iodin. 
To obtain an approximate idea of the amount of hydrocyanic-acid 
gas necessary to saturate the soil at a definite partial pressure of hydro¬ 
cyanic-acid gas, air from the standard solution as above was aspirated 
through a tube containing 50 gm. of soil until no more gas was absorbed. 
At the first titration it required 2,740 c. c. of air when drawn through 
the soil to decolorize 5 c. c. of N/ioo iodin, while 540 c. c. direct from 
the hydrocyanic-acid gas solution gave the same result. The difference 
between the amounts aspirated through the soil and that directly from 
the gas solution gave the total amount of hydrocyanic-acid gas absorbed, 
or adsorbed, or chemically decomposed by the soil, which was equivalent 
to 26 c. c. of N/ioo iodin, in contrast with the equivalent of 31 c. c. of 
N/ioo iodin absorbed by a similar amount of water. Table VIII indi¬ 
cates the gradual approach to the point of saturation. 
Table VIII .—Saturation of soil with hydrocyanic-acid gas 
Character of soil. 
Titration. 
Control. 
Difference. 
Sandy loam. 
C. c. 
2,740 
880 
620 
580 
460 
C.c. 
540 
510 
5*0 
510 
415 
C. c. 
2, 200 
370 
no 
70 
45 
Do... 
Do. 
Do. 
Do. 
Total quantity of air required to saturate soil.... 
2,795 
1 The term “ adsorption * ’ will be used to designate the concentration of two or more heterogeneous phases 
at their contiguous surfaces in contrast with the volume concentrations of these same substances. 
“Absorption ” is the phenomenon of interpenetration of two or more phases until a certain concentration 
in the total volume is reached. 
15755°—17 - 3 
